Method for Preparing Linear Alpha-Olefins with Removal of Aromatic By-Products and Reactor System Therefor

ABSTRACT

The present invention relates to a method and a reactor system for preparing linear alpha-olefins by oligomerization of ethylene in the presence of an organic solvent and an oligomerization catalyst, wherein a product fraction of C 10+  alpha-olefins contaminated with aromatic C 9+  compounds is separated from a product main stream and transferred into a conversion reactor, where C 10+  alpha-olefins and aromatic C 9+  components are reacted in the presence of a Friedel-Crafts alkylation catalyst to produce aromatic C 19+  compounds.

The present invention relates to a method for preparing linearalpha-olefins by oligomerization of ethylene in the presence of anorganic solvent and a catalyst.

Methods for the production of linear alpha-olefins by oligomerization ofethylene are widely known in the art. Usually, a catalyst is utilized inthat process comprising a zirconium component and an organoaluminumcomponent which acts as an activator.

For example, DE 43 38 414 C1 discloses a process for the production oflinear alpha-olefins, wherein one reactor is utilized into which acatalyst solution and ethylene are introduced. That process results in aproduct distribution of linear alpha-olefins having C₄-C₂₈; carbonatoms, wherein the fraction of C₂₀₊ usually contains waxy, polymericsubstances.

The product stream containing alpha-olefins with C₄-C₂₈ carbon atoms maybe separated into fractions, e.g. by distillation or extraction. Onemain fraction obtained is a fraction containing C₁₀₊ alpha-olefins,preferably C₁₀-C₁₈. This fraction may be often contaminated by aromaticcomponents, preferably C₉₊ aromatic components which are formed duringoligomerization. Of course, these by-products are not desired, as a lessvaluable fraction C₁₀₊ is provided. In the prior art, the aromaticcomponents have been so far removed by repeated extraction and/ordistillation, e.g. five distillation columns have been used so far toremove the aromatic components from the C₁₀₊ alpha olefin fraction.

It is therefore an object of the present invention to provide a methodfor preparing linear alpha-olefins which overcomes the drawbacks of theprior art. Especially, a method shall be provided wherein aromaticby-products, commonly present in the C₁₀₊ alpha-olefin fraction, can beeasily removed with low costs, in order to improve the value of the C₁₀₊alpha-olefin fraction.

This object is achieved in that a product fraction of C₁₀₊ alpha-olefinscontaminated with aromatic C₉₊ compounds is separated from a productmain stream and transferred into a conversion reactor, where C₁₀₊alpha-olefins and aromatic C₉₊ components are reacted in the presence ofa Friedel-Crafts alkylation catalyst to produce aromatic C₁₉₊components.

Preferably, the Friedel-Crafts-alkylation catalyst is selected from anymaterial with sufficient acidity to catalyze the alkylation.

More preferably, the Friedel-Crafts-alkylation catalyst is selected fromclay, zeolites, Lewis acids and protonic acids.

In one preferred embodiment, the Friedel-Crafts-alkylation catalyst isselected from clay, zeolite, H₂SO₄, P₄O₁₀, H₃PO₄, AlCl₃, FeCl₃, SbCl₅,SnCl₄, BF₃, TiCl₄ and ZnCl₂.

The aromatic C₁₉₊ compounds prepared may be preferably separated fromunreacted C₁₀₊ alpha-olefins in or downwards the conversion reactor,preferably by distillation.

Moreover, it is preferred that the separated C₁₉₊ compounds are combinedwith C₂₀₊ residue obtained during the oligomerization.

The aromatic C₁₉₊ compounds may be transferred to a further device forthermal use thereof, preferably combustion.

In one preferred embodiment, the conversion in the conversion reactor isconducted at ambient temperature.

Further preferred, additional solvent is added to the fraction of C₁₀₊alpha-olefins prior to introduction into the conversion reactor.

Most preferably, the C₁₀₊ alpha-olefin fraction is a C₁₀-C₁₈ fraction.

The invention further provides a reactor system for oligomerization ofethylene to form linear alpha-olefins, preferably utilizing a methodaccording to the invention, comprising an oligomerization reactor and aconversion reactor, wherein a Friedel-Crafts-alkylation catalyst ispresent in that conversion reactor.

Surprisingly, it was found that the aromatic by-products contained inthe C₁₀₊ linear alpha-olefin fraction can be easily converted (removed)by reacting the C₁₀₊ alpha-olefins with aromatic components, obtained inthe oligomerization process, in the presence of a Friedel-Craftsalkylation catalyst in a separate conversion reactor to produce aromaticcomponents having at least C₁₉₊. These C₁₉₊ aromatic components can beeasily separated from the C₁₀₊ alpha-olefin fraction and can be furtherprocessed, for example, combusted. Thus, the separation of the aromaticby-products is achieved in a very simple method step and safes fivedistillation columns which have been used so far to separate thearomatic by-products from the alpha-olefins fraction. Therefore,investment and operation costs are decreased, and a value added product(alpha-olefin fraction without by-products) is obtained.

As is obvious for someone skilled in the art, the concept of the presentinvention may be also adapted to any hydrocarbon streams containingaromatic impurities or by-products. For example, in case of paraffinicstreams, olefins have to be added into the paraffinic stream to allowthe conversion to heavy aromatic compounds which may be easilyseparated.

In general, the conversion of linear alpha-olefins (C₁₀₊) with aromaticcomponents (C₉₊) is according to the following scheme:

wherein R′ is any alkyl group having two or more carbon atoms and R isany alkyl group having at least eight carbon atoms, preferably eight tosixteen carbon atoms.

Additional advantages and features of the inventive method and reactorsystem are further illustrated with reference to the accompanyingdrawing, wherein FIG. 1 illustrates a schematic diagram of the reactorsystem for carrying out the method according to the present invention.

In FIG. 1 a reactor 1 for the oligomerization of ethylene to preparelinear alpha-olefins is pro-vided. In the reactor 1 ethylene isoligomerized in the presence of a solvent, preferably toluene, and asuitable catalyst, preferably at a temperature of about 60-100° C. Afteroligomerization (the reactor is preferably operated continuously), aproduct stream is removed from the reactor via a discharge line 2. Theproduct stream comprises the solvent, catalyst, liquid linearalpha-olefins and high molecular weight oligomers as well as unreacteddissolved ethylene. The constituents of the product stream may beseparated, e.g. in a separation unit 3. For example, the liquid linearalpha-olefins may be separated into several fractions by distillation toobtain fractions of C₄-C₈, C₁₀-C₁₈ and C₂₀₊. Usually, the fraction ofC₁₀-C₁₈ (C₁₀₊) comprises aromatic by-products. This fraction may betransferred from the separation unit 3 via line 4 into a conversionreactor 5, optional additional solvent may be provided, wherein the C₁₀₊fraction and the aromatic by-products are reacted in the presence of aFriedel-Crafts-allylation catalyst. The discharge stream of theconversion reactor 5 may be then further processed, e.g. the aromaticby-products (now C₁₉₊) can be separated from the alpha-olefins bydistillation and transferred to a further device, e.g. for combustion.The purified C₁₀₊ fraction may be utilized for any desired purpose andhas added value.

The features disclosed in the foregoing description, in the drawing orin the claims may, both separately and in any combination thereof, bematerial for realizing the invention in diverse forms thereof.

1. A method for removing C₉₊ aromatic compounds from the linearalpha-olefins product of the oligomerization of ethylene in the presenceof an organic solvent and an oligomerization catalyst, comprisingseparating the linear alpha-olefins product into molecular weightfractions including at least a C₁₀₊ alpha-olefins fraction whichcomprises C₁₀₊ alpha-olefins and C₉₊ aromatic compounds and thensubjecting the C₁₀₊ alpha-olefins fraction to an alkylation reactionwherein C₁₀₊ alpha-olefins and the C₉₊ aromatic compounds in the C₁₀₊alpha-olefins fractions are reacted in the presence of a Friedel-Craftsalkylation catalyst to produce C₁₉₊ aromatic compounds.
 2. The methodaccording to claim 1, wherein the Friedel-Crafts alkylation catalyst isselected from materials with sufficient acidity to catalyze thealkylation reaction.
 3. The method according to claim 2, wherein theFriedel-Crafts alkylation catalyst is selected from clay, zeolites,Lewis acids and protonic acids.
 4. The method according to claim 2,wherein the Friedel-Crafts alkylation catalyst is selected from clay,zeolite, H₂SO₄, P₄O₁₀, H₃PO₄, AlCl₃, FeCl₃, SbCl₅, SnCl₄, BF₃, TiCl₄ andZnCl₂.
 5. The method according to claim 1, wherein the C₁₉₊ aromaticcompounds prepared are separated from the C₁₀₊ alpha-olefins fractionafter the alkylation reaction.
 6. The method according to claim 5,wherein the C₁₉₊ aromatic compounds are separated from the C₁₀₊alpha-olefins fraction by distillation.
 7. The method according to claim3, wherein the C₁₉₊ aromatic compounds are separated from the C₁₀₊alpha-olefins fraction after the alkylation reaction.
 8. The methodaccording to claim 7, wherein the C₁₉₊ aromatic compounds are separatedfrom the C₁₀₊ alpha-olefins fraction by distillation.
 9. The methodaccording to claim 1, wherein the alkylation reaction is at ambienttemperature.
 10. The method according to claim 9, wherein solvent isadded to the C₁₀₊ alpha-olefins fraction prior to the alkylationreaction.
 11. The method according to claim 1, wherein the C₁₀₊alpha-olefins fraction comprises a C₁₀-C₁₈ alpha-olefins fraction. 12.(canceled)
 13. The method according to claim 6, wherein the alkylationreaction is at ambient temperature.
 14. The method according to claim 8,wherein the alkylation reaction is at ambient temperature.
 15. Themethod according to claim 3, wherein solvent is added to C₁₀₊alpha-olefins fraction prior to the alkylation reaction.
 16. The methodaccording to claim 6, wherein the C₁₀₊ alpha-olefins fraction is aC₁₀-C₁₈ alpha-olefins fraction.
 17. The method according to claim 8,wherein the C₁₀₊ alpha-olefins fraction is a C₁₀-C₁₈ alpha-olefinsfraction.
 18. A reactor system for the production of linearalpha-olefins by the oligomerization of ethylene in the presence of anorganic solvent and an oligomerization catalyst, comprising anoligomerization reactor for the production a linear alpha-olefinproduct, a distillation separator and an alkylation reactor, wherein thelinear alpha-olefins product from the oligomerization reactor isintroduced into the distillation separator, wherein it is separated intoat least two molecular weight fractions which comprise at least a C₁₀₊linear alpha-olefins fraction containing C₁₀₊ alpha-olefins and C₉₊aromatic compounds, and thereafter the C₁₀₊ alpha-olefins fraction isintroduced into the alkylation reactor, wherein C₁₀₊ alpha-olefins arereacted with the C₉₊ aromatic compounds to produce an alkylation reactorproduct comprising C₁₉₊ aromatic compounds.
 19. The reactor system ofclaim 18, further comprising a second distillation separator whichreceives the alkylation reactor product and wherein the alkylationreactor product is separated into at least a C₁₀₊ alpha-olefins fractionand a C₁₉₊ aromatic compounds fraction.